With the progress of the processing ability including the computation speed and the storage capacity of the personal computer (hereinafter referred to as the PC), the capacity of the hard disk drive (hereinafter referred to as the HDD) built in the PC has increased. In this situation, even the PC of the rank used in an ordinary home has come to possess the ability to record a TV broadcast program using the HDD and permit the user to view the recorded program on the display of the PC.
As the result of recent development of the digital video signal processing technique, on the other hand, digital AV equipments such as a TV having a built-in digital tuner for receiving the digital broadcasting (hereinafter referred to as the DTV) and a digital recorder for recording/reproducing a digital broadcast program (for example, the HDD recorder, DVD recorder and the BD recorder) have been commercialized in succession.
Further, the extension of the broadband/internet has made it possible to mount a digital interface such as the wired/wireless LAN (Local Area Network), IEEE1394 or USB in the digital AV equipments and transmit the digital contents through a network.
Generally, in the case where the digitally recorded contents are recorded by transmission from one equipment to another through a network, etc. as described above, the data quality is degenerated less during transmission and a copy (duplicate) of the same quality as the contents in the equipment at the transmitting end can be generated at the receiving end. For the contents with the copyright thereof to be protected, therefore, a measure is required to prevent the illegal creation of a copy of the contents departing from the range of personal use.
In transmitting a content between digital AV equipments, for example, a copy protection method is employed in which the content is encrypted by the content transmission equipment, and the information for decryption is shared with the content reception equipment, so that even if the content is received correctly by an equipment other than the destination content reception equipment, the decryption of the content is prevented, thereby preventing the unlimited copy creation.
An example of the copy protection method employed for the digital AV equipments is a Digital Transmission Content Protection (DTCP) method specifying a method of copy protection on the IEEE1394 bus. In the DTCP method, the contents are managed by being classified into the categories of “copy free”, “copy one generation” and “copy never”. The recorder records only the contents in the category of “copy free” or “copy one generation”, and the content in the category of “copy one generation”, once recorded, is handled as “copy free”. Except for the contents in the category of “copy free”, all the contents are transmitted on a bus after being encrypted at the transmitting end to prevent the contents from being copied in an unlimited manner.
Also in the content transmission by wired or wireless LAN, a DTCP-IP method further strengthened in security is specified by extensively applying DTCP to the IP network. According to the DTCP-IP method, a technique is disclosed to define an in-home network to prevent the unlimited remote distribution of the contents with the copyright thereof to be protected such as a broadcast program recorded in home.
Patent Document 1: JP-A-2005-5821